JP7345720B2 - Vehicle automatic braking system - Google Patents

Description

The present disclosure relates to an automatic braking device for a vehicle.

Patent Document 1 states, ``In a vehicle with two systems (X-shaped system), one system to which the wheel cylinders of the front left wheel and the right rear wheel belong, and the system to which the wheel cylinders of the right front wheel and the rear left wheel belong, during automatic brake control. , each pressure regulating valve is controlled at the same opening so that the hydraulic pressure in the brake hydraulic circuits of both systems is equal, but due to variations in the accuracy of the pressure regulating valves, a difference occurs between the hydraulic pressures of the brake hydraulic circuits of both systems. , yaw direction behavior may occur in the vehicle.In order to suppress this situation, the brake device 1 performs automatic brake control and transmits hydraulic pressure to each wheel cylinder 61, 62 of the left and right front wheels FL, FR. first and second brake hydraulic pressure circuits 11 and 12, a brake actuator 2 that can individually adjust the hydraulic pressure supplied to each wheel cylinder 61 and 62, and a brake control unit 3 that controls the brake actuator 2. , a behavior detection sensor 4 that detects the behavior of the vehicle in the yaw direction, and the brake actuator 2 includes pumps P1 and P2 that increase the hydraulic pressure of each brake hydraulic pressure circuit 11 and 12 during automatic brake control, and It has pressure regulating valves 21 and 22 that individually adjust the hydraulic pressure of the circuits 11 and 12, and the brake control unit 3 selects the wheel cylinder 61 with the lower braking force based on the behavior in the yaw direction during automatic brake control. "The pressure regulating valves 21 and 22 are controlled so as to increase the hydraulic pressure supplied to the hydraulic pressure 62."

By the way, vehicle deflection during execution of automatic brake control (automatic brake control) is not limited to vehicles that use the X method (also called the "diagonal method") brake piping, but also applies to vehicles that use the front-rear method (also called the "II method"). This can also occur in vehicles that use brake piping. In a front-rear braking system, the hydraulic pressure of the front wheel brake system is adjusted by a pressure regulating valve on one side, and the hydraulic pressure of the rear wheel system is controlled by a pressure regulating valve on the other side. Therefore, vehicle deflection does not occur due to left-right differences in braking force caused by variations in the pressure regulating valves. For example, in a vehicle with a front-rear braking system, the deflection is caused by a deviation in the position of the center of gravity of the vehicle. Specifically, in a truck, a commercial van, etc., when the load loaded on the vehicle is one load, vehicle deflection may occur during execution of automatic braking control. Here, "unbalanced load" refers to a state in which the load loaded on the vehicle is biased in the vehicle width direction. In order to suppress vehicle deflection caused by unbalanced loads, the applicant has developed devices described in Patent Documents 2 and 3.

In these devices, braking control for suppressing vehicle deflection is performed based on a preset threshold. The threshold value depends on the vehicle specifications (mass, wheelbase, tread, height of center of gravity). Therefore, it is necessary to adapt it to each type of vehicle, which requires a considerable amount of development man-hours. There is a desire for an automatic braking system that can be easily adapted to each vehicle type.

JP2017-149378 Patent Application No. 2019-002073 Patent Application No. 2019-002074

An object of the present invention is to provide an automatic braking system for a vehicle in which braking control for suppressing vehicle deflection is executed, in which adaptation of the braking control can be easily performed.

An automatic braking device for a vehicle according to the present invention executes deflection suppression control that suppresses deflection of the vehicle during braking by adjusting the braking force (Fx) of each wheel (WH) of the vehicle, and The amount of deflection (Hn) representing the degree of deflection of the vehicle is calculated, and the amount of deflection (Hn) representing the degree of deflection of the vehicle is estimated from the vehicle body speed (Vx) of the vehicle and the deceleration (Ga) of the vehicle from the current time until the vehicle stops. A threshold value (Hx) for starting the deflection suppression control is determined based on the lateral movement distance . Then, the deflection suppression control is started when the deflection amount (Hn) becomes equal to or greater than the threshold value (Hx).

According to the above configuration, the threshold value Hx for starting the deflection suppression control is determined as a state variable that can be detected or calculated. Therefore, adaptation to each vehicle type is easy, and the number of man-hours required for adaptation can be reduced.

1 is an overall configuration diagram for explaining an embodiment of an automatic braking device JS for a vehicle according to the present invention. FIG. 3 is a flow diagram for explaining calculation processing of automatic braking control including deflection suppression control. FIG. 2 is a schematic diagram for explaining calculation processing of a deflection amount Hn and a starting threshold value Hx.

<Symbols of component parts, subscripts at the end of the symbol, and direction of movement/movement>
In the following description, components, arithmetic processing, signals, characteristics, and values having the same symbol, such as "CW", have the same function. The subscripts "i" to "l" added to the end of each symbol are comprehensive symbols indicating which wheel the symbol relates to. Specifically, "i" indicates the right front wheel, "j" indicates the left front wheel, "k" indicates the right rear wheel, and "l" indicates the left rear wheel. For example, the four wheel cylinders are expressed as a right front wheel cylinder CWi, a left front wheel cylinder CWj, a right rear wheel cylinder CWk, and a left rear wheel cylinder CWl. Furthermore, the subscripts “i” to “l” at the end of the symbol may be omitted. If the subscripts "i" to "l" are omitted, the symbol represents a general term for each of the four wheels. For example, "CW" represents a wheel cylinder provided at each wheel WH.

The suffixes "f" and "r" added to the end of each symbol are comprehensive symbols indicating which symbol the symbol refers to in the longitudinal direction of the vehicle. Specifically, "f" indicates the front wheel, and "r" indicates the rear wheel. For example, the wheels are expressed as a front wheel WHf and a rear wheel WHr. Furthermore, the subscripts "f" and "r" at the end of the symbol may be omitted. When the subscripts "f" and "r" are omitted, each symbol represents its generic name. "CWf (=CWi, CWj)" represents the front wheel cylinder, and "CWr (=CWk, CWl)" represents the rear wheel cylinder.

In the connection path HS, the side closer to the master reservoir RV is called the "upper" and the side closer to the wheel cylinder CW is called the "lower". In addition, in the reflux KN in which the brake fluid BF circulates, the side closer to the discharge part Bt of the fluid pump HP is called the "upstream side (upstream part)", and the side far from the discharge part Bt is called the "downstream side (downstream part)". be done.

<Embodiment of automatic braking device for vehicle according to the present invention>
An embodiment of an automatic braking system JS for a vehicle according to the present invention will be described with reference to the overall configuration diagram of FIG. A vehicle employs two fluid paths (ie, two braking systems). Of the two braking systems, the front wheel braking system BKf (system related to the front wheel master cylinder chamber Rmf) is connected to the right front wheel and the left front wheel cylinder CWi, CWj (=CWf). Further, of the two braking systems, the rear wheel braking system BKr (system related to the rear wheel master cylinder chamber Rmr) is connected to the right rear wheel and the left rear wheel cylinder CWk, CWl (=CWr). A so-called front and rear type (also referred to as "Type II") brake system is used as two braking systems for a vehicle. Here, the "fluid path" is a path for moving the brake fluid BF, which is a working fluid, and includes brake piping, a flow path of the fluid unit HU, a hose, and the like.

A vehicle equipped with the automatic braking device JS is equipped with a brake operating member BP, a wheel cylinder CW, a master reservoir RV, a master cylinder CM, and a brake booster VB. The brake operation member (eg, brake pedal) BP is a member operated by the driver to decelerate the vehicle. By operating the brake operation member BP, the hydraulic pressure (also referred to as "braking hydraulic pressure") Pw of the wheel cylinder CW is adjusted, the braking torque Tq of the wheel WH is adjusted, and the braking force Fx is generated at the wheel WH. Ru.

A rotating member (for example, a brake disc) KT is fixed to the wheel WH of the vehicle. A brake caliper is arranged to sandwich the rotating member KT. The brake caliper is provided with a wheel cylinder CW, and by increasing the pressure of the brake fluid BF (braking fluid pressure) Pw inside the wheel cylinder CW, a friction member (for example, a brake pad) is pressed against the rotating member KT. Since the rotating member KT and the wheel WH are fixed so as to rotate integrally, the braking torque Tq is generated at the wheel WH due to the frictional force generated at this time. This braking torque Tq generates a braking force Fx on the wheel WH.

The master reservoir (an atmospheric pressure reservoir, also simply referred to as "reservoir") RV is a tank for working fluid, and brake fluid BF is stored therein. When the amount of brake fluid BF is insufficient in master cylinder CM, brake fluid BF is replenished from master reservoir RV to master cylinder chamber (also referred to as "hydraulic pressure chamber") Rm.

Inside the master cylinder CM, two hydraulic chambers Rmf and Rmr are formed by a primary piston PG and a secondary piston PH. In other words, a tandem type master cylinder CM is used. The piston PG in the master cylinder CM is mechanically connected to the brake operation member BP via a brake rod, a brake booster VB, etc. When the brake operation member BP is not operated, the front wheel and rear wheel hydraulic pressure chambers Rmf and Rmr (=Rm) of the master cylinder CM are in communication with the master reservoir RV.

The brake booster (also simply referred to as "booster") VB reduces the operating force Fp of the brake operating member BP by the driver. A negative pressure type booster is used as the booster VB. Negative pressure is generated by an engine or an electric negative pressure pump. As the booster VB, one using an electric motor as a driving source may be employed (for example, an electric booster, an accumulator type hydraulic booster).

Furthermore, the vehicle includes a wheel speed sensor VW, a steering operation amount sensor SA, a yaw rate sensor YR, a longitudinal acceleration sensor (also referred to as a "deceleration sensor") GX, a lateral acceleration sensor GY, a braking operation amount sensor BA, and a distance sensor. OB will be provided. Each wheel WH of the vehicle is equipped with a wheel speed sensor VW to detect the wheel speed Vw. The signal of the wheel speed Vw is used for independent control of each wheel, such as anti-lock brake control, which suppresses the tendency of the wheels WH to lock (ie, excessive deceleration slip).

The steering operation member (eg, steering wheel) SW is equipped with a steering operation amount sensor (eg, steering angle sensor) SA to detect the steering amount (eg, steering angle) Sa. The body of the vehicle is equipped with a yaw rate sensor YR to detect a yaw rate (yaw angular velocity) Yr. In addition, acceleration in the longitudinal direction (direction of travel) of the vehicle (longitudinal acceleration, also referred to as "detected deceleration"), and acceleration in the lateral direction (direction perpendicular to the direction of travel) (lateral acceleration, also referred to as "detected deceleration") A longitudinal acceleration sensor GX and a lateral acceleration sensor GY are provided to detect Gy (also referred to as "lateral acceleration"). Detection signals from these sensors are used for vehicle motion control such as vehicle stabilization control (so-called ESC) that suppresses excessive oversteer behavior and understeer behavior.

A brake operation amount sensor BA is provided to detect an operation amount Ba of a brake operation member BP (brake pedal) by the driver. The brake operation amount sensor BA includes a master cylinder hydraulic pressure sensor PM that detects the hydraulic pressure (master cylinder hydraulic pressure) Pm in the master cylinder CM, an operation displacement sensor SP that detects the operation displacement Sp of the brake operation member BP, and a brake. At least one of the operating force sensors FP that detects the operating force Fp of the operating member BP is employed. That is, the operation amount sensor BA detects at least one of the master cylinder hydraulic pressure Pm, the operation displacement Sp, and the operation force Fp as the braking operation amount Ba.

Wheel speed Vw, steering operation amount (steering angle) Sa, yaw rate Yr, longitudinal acceleration (detected deceleration) Gx, lateral acceleration (detected lateral acceleration) Gy, and braking operation amount Ba detected by each sensor (VW, etc.) is input to the brake controller ECU. The brake controller ECU calculates the vehicle speed Vx based on the wheel speed Vw.

≪Driving support system≫
Vehicles are equipped with driving support systems to avoid collisions with obstacles or reduce damage in the event of a collision. The driving support system includes a distance sensor OB and a driving support controller ECJ. The distance sensor OB detects the distance (relative distance) Ob between the own vehicle and an object (another vehicle, a fixed object, a person, a bicycle, etc.) that exists in front of the own vehicle. For example, an image sensor (camera), a radar sensor, or the like is employed as the distance sensor OB. The relative distance Ob is input to the driving support controller ECJ.

The driving support controller ECJ calculates the required deceleration Gs based on the relative distance Ob. The required deceleration Gs is a target value of vehicle deceleration for executing automatic braking control. The requested deceleration Gs is transmitted to the brake controller ECU via the communication bus BS.

For example, the required deceleration Gs is calculated based on the collision margin time Tc and the headway time Tw. Collision margin time Tc is the time until a collision occurs between the host vehicle and an object. '' and is determined by dividing by the time derivative value of the relative distance Ob. The headway time Tw is the time taken for the own vehicle to reach the current position of the object in front, and is calculated by dividing the relative distance Ob by the vehicle speed Vx. The required deceleration Gs is calculated to become smaller as the collision margin time Tc becomes larger. Further, the required deceleration Gs is calculated such that the larger the headway time Tw is, the smaller the required deceleration Gs is.

≪Brake controller ECU≫
The automatic braking device JS includes a brake controller ECU and a fluid unit HU. The brake controller (also referred to as "electronic control unit") ECU includes an electric circuit board on which a microprocessor MP and the like are mounted, and a control algorithm programmed into the microprocessor MP. The controller ECU is network-connected to other controllers (ECJ, etc.) via an on-vehicle communication bus BS so as to share signals (detected values, calculated values, etc.). For example, the brake controller ECU is connected to the driving support controller ECJ through the communication bus BS. The vehicle speed Vx is transmitted from the brake controller ECU to the driving support controller ECJ. On the other hand, the driving support controller ECJ sends the required deceleration Gs (target value) is sent.

A brake controller ECU (electronic control unit) controls an electric motor MT of a fluid unit HU and three different types of solenoid valves UA, VI, and VO. Specifically, drive signals Ua, Vi, and Vo for controlling the various electromagnetic valves UA, VI, and VO are calculated based on a control algorithm within the microprocessor MP. Similarly, a drive signal Mt for controlling electric motor MT is calculated.

The controller ECU is equipped with a drive circuit DR to drive the electromagnetic valves UA, VI, VO and the electric motor MT. A bridge circuit is formed in the drive circuit DR by switching elements (power semiconductor devices such as MOS-FET and IGBT) to drive the electric motor MT. Based on the motor drive signal Mt, the energization state of each switching element is controlled, and the output of the electric motor MT is controlled. Further, in the drive circuit DR, the energization state (that is, the excitation state) of the electromagnetic valves UA, VI, and VO is controlled by switching elements based on the drive signals Ua, Vi, and Vo to drive the electromagnetic valves UA, VI, and VO. Note that the drive circuit DR is provided with an energization amount sensor that detects the actual energization amount of the electric motor MT and the solenoid valves UA, VI, and VO. For example, a current sensor is provided as the energization amount sensor to detect the current supplied to the electric motor MT and the solenoid valves UA, VI, and VO.

The braking operation amount Ba (Pm, Sp, etc.), wheel speed Vw, yaw rate Yr, steering angle Sa, longitudinal acceleration (detected deceleration) Gx, and lateral acceleration (detected lateral acceleration) Gy are input to the brake controller ECU. Further, the required deceleration Gs is input to the brake controller ECU from the driving support controller ECJ via the communication bus BS. Based on the required deceleration Gs, the brake controller ECU executes automatic brake control including deflection suppression control (described later) to avoid a collision with an obstacle or reduce damage in the event of a collision.

≪Fluid unit HU≫
The fluid unit HU is an actuator that individually controls the braking force Fx of each wheel WH. The fluid unit HU includes an electric motor MT, a fluid pump HP, a pressure regulating reservoir RC, a pressure regulating valve UA, a master cylinder hydraulic pressure sensor PM, an inlet valve VI, and an outlet valve VO.

The front and rear wheel hydraulic pressure chambers Rmf and Rmr and the front and rear wheel cylinders CWf and CWr are connected through front and rear wheel connecting paths (one of the fluid paths) HSf and HSr (=HS). A fluid unit HU is connected to the connection path HS. The connection path HS is branched at locations Bbf and Bbr within the fluid unit HU, and is connected to front and rear wheel cylinders CWf (=CWi, CWj) and CWr (=CWk, CWl). Front wheel, rear wheel pressure regulating valves UAf, UAr (portion of connection path HS between pressure regulating valve UA and hydraulic pressure chamber Rm) upper part Bmf, Bmr, front wheel, rear wheel pressure regulating valves UAf, UAr (pressure regulating valve UA and inlet valve) The lower portions Bbf and Bbr of the connection path HS with VI are connected to the front wheel and rear wheel return paths HKf and HKr (=HK). Front and rear wheel fluid pumps HPf and HPr, and front and rear wheel pressure regulating reservoirs RCf and RCr are provided in the front and rear wheel recirculation paths HKf and HKr.

Two fluid pumps (front wheel and rear wheel fluid pumps) HPf and HPr (=HP) are driven by one electric motor MT. Electric motor MT is controlled based on a drive signal Mt from a brake controller ECU. The fluid pump HP draws brake fluid BF from the front and rear wheel pressure regulation reservoirs RCf and RCr (=RC) at the suction parts Bsf and Bsr located upstream of the front and rear wheel pressure regulation valves UAf and UAr (=UA). is pumped up. The pumped brake fluid BF is discharged to the front and rear wheel discharge portions Btf and Btr located downstream of the front and rear wheel pressure regulating valves UAf and UAr.

Front wheel and rear wheel pressure regulating valves UAf and UAr (=UA) are provided in front wheel and rear wheel connection paths HSf and HSr. The pressure regulating valve UA is a linear solenoid valve (also referred to as a "proportional valve" or "differential pressure valve") whose opening amount (lift amount) is continuously controlled based on the energization state (for example, supply current). will be adopted. The pressure regulating valve UA is controlled based on a drive signal Ua from the brake controller ECU. Here, normally open electromagnetic valves are employed as the front wheel and rear wheel pressure regulating valves UAf, UAr.

In the controller ECU, a target energization amount (for example, target current) of the pressure regulating valve UA is determined based on the calculation results of automatic braking control and the like (for example, the reference hydraulic pressure of the wheel cylinder CW). A drive signal Ua is determined based on the target energization amount, and in accordance with this drive signal Ua, the energization amount (current value) to the pressure regulating valve UA is adjusted, and the opening amount of the pressure regulating valve UA is adjusted.

When the fluid pump HP is driven, the reflux of the brake fluid BF from "RC→HP→UA→RC" (flow of the circulating brake fluid BF indicated by the broken line arrow) KN occurs in the reflux path HK and the connection path HS. It is formed. When the pressure regulating valve UA is not energized and the normally open pressure regulating valve UA is fully open, the hydraulic pressure at the upstream section Bm of the pressure regulating valve UA (i.e., the master cylinder hydraulic pressure Pm) and the pressure regulating valve UA are equal to each other. The hydraulic pressure Pp (referred to as "adjusted hydraulic pressure") of the downstream portion Bb substantially matches.

The amount of current applied to the normally open pressure regulating valve UA is increased, and the amount of opening of the pressure regulating valve UA is decreased. The pressure regulating valve UA throttles the recirculation KN of the brake fluid BF, and a pressure difference (differential pressure) is generated between the upstream portion Bm and the downstream portion Bb of the pressure regulating valve UA. That is, due to the orifice effect of the pressure regulating valve UA, the downstream hydraulic pressure (adjusted hydraulic pressure) Pp is adjusted by increasing from the upstream hydraulic pressure (master cylinder hydraulic pressure) Pm. When the brake operation member BP is not operated, "Pm = 0", but the brake fluid pressure (wheel cylinder fluid pressure) Pw is increased from "0" by the adjustment fluid pressure Pp, and automatic braking is activated. It will be done.

Front and rear wheel master cylinder hydraulic pressure sensors PMf and PMr are provided in the connection path HS above the pressure regulating valve UA to detect front and rear wheel master cylinder hydraulic pressures Pmf and Pmr. In addition, since "Pmf=Pmr" basically, one of the front wheel and rear wheel master cylinder hydraulic pressure sensors PMf and PMr can be omitted.

The front wheel and rear wheel connecting paths HSf and HSr are branched (divided) at the lower portions Bbf and Bbr of the front and rear wheel pressure regulating valves UAf and UAr, and are connected to each of the wheel cylinders CWi to CWl. At the lower part of the branch portions Bbf and Bbr, the configuration related to each wheel WH (=WHi to WHl) is the same.

An inlet valve VI (=VIi to VIl) is provided in the connection path HS (=HSi to HSl) below the branch portions Bbf and Bbr. A normally open on/off solenoid valve is used as the inlet valve VI. The connection path HS is connected to the front wheel and rear wheel pressure reduction paths HGf and HGr (=HG) at the lower part of the inlet valve VI (that is, between the inlet valve VI and the wheel cylinder CW). Further, the pressure reducing path HG is connected to the pressure regulating reservoir RC (=RCf, RCr). The pressure reduction path HG is provided with an outlet valve VO (=VOi to VOl). A normally closed on/off solenoid valve is used as the outlet valve VO.

In order to reduce the hydraulic pressure (braking hydraulic pressure) Pw in the wheel cylinder CW by anti-lock brake control, the inlet valve VI is placed in the closed position and the outlet valve VO is placed in the open position. The inflow of the brake fluid BF from the inlet valve VI is blocked, the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RC, and the brake fluid pressure Pw is reduced. Furthermore, in order to increase the brake fluid pressure Pw, the inlet valve VI is placed in the open position, and the outlet valve VO is placed in the closed position. The outflow of the brake fluid BF to the pressure regulation reservoir RC is prevented, the regulation hydraulic pressure Pp is introduced into the wheel cylinder CW, and the brake fluid pressure Pw is increased. Furthermore, in order to maintain the hydraulic pressure (braking hydraulic pressure) Pw in the wheel cylinder CW, both the inlet valve VI and the outlet valve VO are closed. That is, by controlling the electromagnetic valves VI and VO, the braking fluid pressure Pw (that is, the braking torque Tq, and as a result, the braking force Fx) can be adjusted independently by the wheel cylinder CW of each wheel WH.

<Automatic braking control calculation processing>
Automatic braking control processing including deflection suppression control will be described with reference to the flowchart in FIG. 2 . This process is performed by the brake controller ECU. "Automatic braking control" is based on the object (obstacle) in front of the vehicle and the required deceleration Gs according to the relative distance Ob between the vehicle and the wheel cylinder to avoid collision between the vehicle and the obstacle. The CW hydraulic pressure (braking hydraulic pressure) Pw (=Pwi to Pwl) is increased from the master cylinder CM hydraulic pressure (master cylinder hydraulic pressure) Pm (=Pmf, Pmr). "Deflection suppression control" is a system that independently controls the vehicle deflection that occurs during execution of automatic braking control (that is, during automatic braking) by controlling the braking force Fx (=Fxi to Fxl) of each wheel WH (=WHi to WHl). It is suppressed through regulation.

In step S110, various signals are read. Specifically, required deceleration Gs, detected deceleration Gx (detected value of deceleration sensor GX), yaw rate Yr, detected lateral acceleration Gy (detected value of lateral acceleration sensor GY, also simply referred to as "lateral acceleration"). ) and the steering angle Sa are acquired (detected or received).

In step S120, the vehicle body speed Vx and the actually occurring deceleration (actual deceleration, also simply referred to as "deceleration") Ga of the vehicle are calculated. Vehicle speed Vx is calculated based on wheel speed Vw. For example, when the vehicle is not braking, including when the vehicle is accelerating, the vehicle body speed Vx is calculated based on the slowest wheel speed among the four wheel speeds Vw. Furthermore, during braking, the vehicle body speed Vx is calculated based on the fastest wheel speed among the four wheel speeds Vw. Furthermore, in calculating the vehicle speed Vx, a limit may be set on the amount of change over time. That is, an upper limit value αup of the increasing slope of the vehicle body speed Vx and a lower limit value αdn of the decreasing slope are set, and changes in the vehicle body speed Vx are restricted by the upper and lower limit values αup and αdn.

The actual deceleration (actual deceleration) Ga is the acceleration that actually occurs in the direction of decelerating the vehicle in the longitudinal direction (progressing direction) of the vehicle. The actual deceleration Ga is calculated based on at least one of the detected deceleration Gx and the time differential value of the vehicle body speed Vx (referred to as "calculated deceleration Ge"). Note that for the required deceleration Gs, the actual deceleration Ga, the detected deceleration Gx, and the calculated deceleration Ge, the value on the side that decelerates the vehicle is represented by a "plus sign (+)".

In step S130, it is determined whether automatic braking control is necessary. For example, whether or not this is necessary is determined based on a comparison between the required deceleration Gs and the actual deceleration Ga. If "Gs≦Ga", automatic braking control is not necessary, and the process returns to step S110. If "Gs>Ga", it is determined that automatic braking control is necessary, and the process proceeds to step S140.

In step S140, the standard turning amount Ys and the actual turning amount Ya are calculated, and the turning amount deviation hY is calculated based on them. Specifically, the standard turning amount Ys is calculated based on the steering amount (steering angle) Sa, and the actual turning amount Ya is calculated based on the yaw rate Yr. Then, a turning amount deviation hY is calculated based on the standard turning amount Ys and the actual turning amount Ya. The turning amount deviation hY is a state quantity that represents the difference between the actual direction of travel of the vehicle (ie, the actual amount of turning Ya) from the direction of travel of the vehicle instructed by the steering amount Sa (ie, the reference amount of turning Ys). Therefore, the deflection state of the vehicle is expressed by the turning amount deviation hY.

The turning amount deviation hY is calculated using the following equation (1), taking into account the turning direction of the vehicle.
hY=sgn(Yr)・(Ya−Ys)…Formula (1)
Here, the function "sgn" is a sign function (also referred to as a "signum function"), and is a function that returns either "1", "-1", or "0" depending on the sign of the argument. For example, if the left turning direction is a positive sign (+) and the right turning direction is a negative sign (-), "sgn(Yr)=1" is calculated for a left turning, and for a right turning "sgn(Yr)=-1" is calculated. Therefore, when the vehicle is traveling straight (that is, "Sa=Ys=0") and is deflected to the left, "sgn(Yr)" is a positive sign (+) and "Ya-Ys ” becomes a plus sign (+), so “hY” becomes a plus sign (+). Conversely, when deflecting to the right, "sgn(Yr)" has a negative sign (-) and "Ya-Ys" has a negative sign (-), so "hY" has a positive sign (+ )become.

For example, the yaw rate Yr is employed as the physical quantity of the turning amount deviation hY, and the yaw rate deviation hY is calculated. In this case, the standard turning amount Ys is based on the steering angle Sa and the vehicle speed Vx, when the steering gear ratio is "N", the wheelbase is "L", and the stability factor is "Kh" in the vehicle. It is calculated using the following formula (2).
Ys=(Vx×Sa)/{N×L×(1+Kh・Vx ² )}...Formula (2)
Further, as the actual turning amount Ya, the yaw rate Yr (detected yaw rate) detected by the yaw rate sensor YR is used as is. Here, the standard turning amount Ys corresponds to a case where the grip state of the wheels WH is appropriate.

When the wheels WH are gripping, the steering angle Sa and the yaw rate Yr have a predetermined relationship. Therefore, the turning amount deviation hY may be calculated in the dimension of the steering angle Sa as a physical quantity. The turning amount deviation hY in this case is called a "steering angle deviation". When the dimension of the steering angle Sa is employed as the physical quantity, the steering angle Sa is directly determined as the standard turning amount Ys. Further, the actual turning amount Ya is calculated using the following equation (3).
Ya={N×L×(1+Kh・Vx ² )×Yr}/Vx…Formula (3)
In any case, the turning amount deviation hY is calculated as the difference between the standard turning amount Ys according to the steering amount Sa and the actual turning amount Ya according to the yaw rate Yr.

In step S150, front wheel and rear wheel reference hydraulic pressures Psf and Psr (=Ps) are determined based on the required deceleration Gs. The reference hydraulic pressure Ps is a state quantity that serves as a reference for target values related to the actual front wheel and rear wheel adjustment hydraulic pressures Ppf and Ppr. For example, the front wheel and rear wheel reference hydraulic pressures Psf and Psr are calculated to be the same, and the actual hydraulic pressures (braking hydraulic pressures) Pw (=Pp) of the four wheel cylinders CWi to CWl are instructed to be the same. Ru.

In step S160, it is determined whether or not deflection suppression control is to be executed. Specifically, first, based on "at least one of lateral acceleration Gy and yaw rate Yr", vehicle speed Vx, and (actual) deceleration Ga, the lateral velocity of the vehicle at the time the vehicle stops is determined. The amount of movement Dh (referred to as "lateral movement distance") in the direction (vehicle width direction, transverse direction of the road) is calculated. Then, based on the lateral movement distance Dh, a threshold value (start threshold value, also simply referred to as "threshold value") Hx for starting deflection suppression control is determined. A state quantity (referred to as "deflection amount Hn", for example, turning amount deviation hY) representing the degree (extent) of vehicle deflection calculated based on at least one of lateral acceleration Gy and yaw rate Yr is The start of deflection suppression control is determined depending on whether or not the threshold value Hx is greater than or equal to the start threshold value Hx. Details of the calculation of the deflection amount Hn and the threshold value Hx will be described later.

In step S160, if the deflection amount Hn is less than the start threshold value Hx, no vehicle deflection has occurred. Therefore, if "Hn<Hx", the process proceeds to step S170. If the deflection amount Hn is greater than or equal to the start threshold Hx, vehicle deflection has occurred, and the process proceeds to step S180.

In step S170, final front wheel and rear wheel target hydraulic pressures Ptf and Ptr (=Pt) are calculated. Step S170 corresponds to processing in which vehicle deflection does not occur in automatic braking control. Therefore, the reference hydraulic pressure Ps is directly determined as the target hydraulic pressure Pt (ie, "Pt=Ps").

In step S180, correction amounts (increase and decrease correction amounts) Pz and Pg related to the hydraulic pressure are calculated based on the calculation maps Zpz and Zpg of the correction amount calculation block ZG shown in the balloon and the turning amount deviation hY. Ru. The incremental correction amount Pz is a state quantity for calculating the front wheel target hydraulic pressure Ptf by increasing the front wheel reference hydraulic pressure Psf. The increase correction amount Pz is calculated to be "0" according to the increase calculation map Zpz when the turning amount deviation hY (or its absolute value) is less than the predetermined amount hx, and the turning amount deviation hY (or its absolute value) is greater than or equal to the predetermined amount hx, the incremental correction amount Pz is calculated to increase from "0" as the absolute value of the turning amount deviation hY increases. The decrease correction amount Pg is a state quantity for calculating the rear wheel target hydraulic pressure Ptr by decreasing the rear wheel reference hydraulic pressure Psr. The reduction correction amount Pg is calculated to "0" in the case of "hY<hx" according to the reduction calculation map Zpg, and in the case of "hY≧hx", the reduction correction amount is calculated as the turning amount deviation hY increases. It is calculated so that Pg increases from "0". Note that upper limit values pz and pg are set for the increase and decrease correction amounts Pz and Pg. Here, the predetermined amount hx is a value obtained by converting the start threshold value Hx into the dimension of the turning amount deviation hY.

In step S190, the front and rear wheel reference hydraulic pressures Psf and Psr (=Ps) are corrected by the increase and decrease correction amounts Pz and Pg, and the final front and rear wheel target hydraulic pressures Ptf and Ptr are calculated. . Specifically, the front wheel target hydraulic pressure Ptf is determined by adding the increase correction amount Pz to the front wheel reference hydraulic pressure Psf (that is, "Ptf=Psf+Pz"). The rear wheel target hydraulic pressure Ptr is determined by subtracting the reduction correction amount Pg from the rear wheel reference hydraulic pressure Psr (ie, "Ptr=Ps-Pg"). Since the rear wheel reference hydraulic pressure Ptr is adjusted to decrease, the rear wheel braking force is reduced, and when the sideslip angle of the rear wheel WHr increases in response to vehicle deflection, a lateral force on the rear wheel WHr is more likely to be generated. , vehicle deflection is suppressed.

In step S200, it is determined (identified) whether "the deflection direction of the vehicle is leftward or rightward." For example, the identification is performed based on the sign of the yaw rate Yr. Alternatively, the identification may be made according to the sign of the turning amount deviation hY calculated based on the yaw rate Yr. If the deflection direction is to the left, the process proceeds to step S210. On the other hand, if the deflection direction is rightward, the process proceeds to step S220.

In step S210, the right front wheel inlet valve VIi is placed in the open position, and the left front wheel inlet valve VIj is placed in the closed position. Since the inlet valve VI is a normally open type, in step S210, the right front wheel inlet valve VIi remains de-energized, and the left front wheel inlet valve VIj is instructed to be energized. Since the front wheel adjustment hydraulic pressure Ppf is increased, the brake hydraulic pressure Pwi of the right front wheel WHi is increased, and the brake hydraulic pressure Pwj of the left front wheel WHj is maintained. The left-right difference in front wheel braking force that occurs at this time suppresses the vehicle from deflecting to the left.

In step S220, the right front wheel inlet valve VIi is placed in the closed position, and the left front wheel inlet valve VIj is placed in the open position. In step S220, the right front wheel inlet valve VIi is instructed to be energized, and the left front wheel inlet valve VIj remains de-energized. Since the brake hydraulic pressure Pwi of the right front wheel WHi is maintained and the brake hydraulic pressure Pwj of the left front wheel WHj is increased, the vehicle deflection to the right is suppressed due to the left-right difference in front wheel braking force.

In step S230, electric motor MT is driven. As a result, a reflux KN of the brake fluid BF including the pressure regulating valve UA and the fluid pump HP (a flow of the brake fluid BF circulating in "HP→UA→RC→HP") is generated.

In step S240, the front and rear wheel pressure regulating valves UAf and UAr (=UA) are controlled based on the front and rear wheel target hydraulic pressures Ptf and Ptr (=Pt). Specifically, a target amount of energization It to the pressure regulating valve UA is determined based on the target hydraulic pressure Pt, and an actual amount of energization Ia to the pressure regulating valve UA is controlled. For example, the drive circuit DR is provided with an energization amount sensor (for example, a current sensor) that detects the actual energization amount Ia, so that the actual energization amount (actual current) Ia matches the target energization amount (target current) It. Servo control (current feedback control) is performed. Further, in controlling the pressure regulating valve UA, servo control (deceleration feedback control) may be performed so that the actual deceleration Ga matches the required deceleration Gs.

Steps S180 to S220 correspond to execution of deflection suppression control that suppresses vehicle deflection during execution of automatic braking control. In this series of processes, the front and rear wheel reference hydraulic pressures Psf and Psr are corrected based on the turning amount deviation hY, and the final front and rear wheel target hydraulic pressures Ptf and Ptr are calculated. In addition, the open/close state of the front wheel inlet valve VIf is controlled.

<Calculation of deflection amount Hn and starting threshold Hx>
Details of the calculation of the deflection amount Hn (a state variable indicating the degree of vehicle deflection) and the start threshold value Hx will be described with reference to the schematic diagram of FIG. 3. In FIG. 3, in a situation where the vehicle is traveling in the center of the driving lane, automatic braking control is started at position (O), and then deflection suppression control is started at position (P). Then, the vehicle is stopped at position (S) by automatic braking control. The displacement (lateral movement distance) Dh in the vehicle width direction (also the cross direction of the road) for each hour is calculated using the following equation (4).
Dh=(1/2)・Gy・(Vx/Ga) ² ...Equation (4)
Equation (4) indicates that the lateral movement distance Dh can be calculated using state variables (Gy, Vx, Ga, etc.) that can be detected or calculated. When formula (4) is transformed, the following formula (5) is obtained.
Gy=2・Dh・(Ga/Vx) ² ...Formula (5)

Taking into consideration the relationship in equation (5), the position where the vehicle stops (S) (that is, the position corresponding to "Vx = 0") is set so that it stays within the driving lane (or does not deviate from the shoulder of the driving road). As a state variable related to the lateral acceleration Gy, a starting threshold value Hx is calculated by the following equation (6).
Hx=2・hd・(Ga/Vx) ² ...Equation (6)
Here, "hd" is a length corresponding to the width direction ("transverse direction", also referred to as "width direction") of the road on which the vehicle is traveling, and is referred to as "predetermined distance". Regarding the magnitude relationship between the predetermined distance hd and the lateral movement distance Dh, the lateral movement distance Dh is smaller than the predetermined distance hd. Therefore, by calculating the start threshold value Hx using the above equation (6), the vehicle can be stopped without running out of the lane (or road shoulder) LE.

The road width (road width) De is specified by laws and regulations. For example, the predetermined distance hd is determined as a preset constant (for example, a value less than "1/2" of the road width De). Further, the edge of the road (a lane, for example, a white line, a road shoulder, etc.) LE may be recognized by an on-vehicle camera, and the predetermined distance hd may be determined based on the recognition result. Furthermore, the current position of the vehicle obtained by the global positioning system (so-called GPS) is checked against map data, and the road width De is obtained based on the information stored in this map data. A predetermined distance hd may be determined.

In the deflection suppression control, the lateral acceleration Gy is employed as the deflection amount Hn. Further, the start threshold Hx is calculated as a state variable in the dimension (the same physical quantity) of the lateral acceleration Gy using equation (6). Then, when the deflection amount Hn (=Gy) becomes equal to or greater than the start threshold value Hx, execution of the deflection suppression control is permitted and started. That is, step S160 is affirmed at the time (calculation cycle) when "Gy≧Hx" is satisfied. After that point, the braking force Fx of each wheel WH is controlled based on the turning amount deviation hY, and the deflection of the vehicle is suppressed. That is, the start of the deflection suppression control is determined based on the lateral acceleration Gy, and the execution of the deflection suppression control is continued based on the turning amount deviation hY.

Since the yaw rate Yr and the lateral acceleration Gy have the relationship of "Gy=Yr·Vx", equation (5) is transformed as follows.
Yr=2・Dh・(Ga ² /Vx ³ )...Formula (7)
In this case, the yaw rate Yr is employed as the deflection amount Hn, and the start threshold value Hx is calculated as a state variable related to the yaw rate Yr using the following equation (8).
Hx=2・hd・(Ga ² /Vx ³ )...Formula (8)
In the deflection suppression control, execution of the deflection suppression control is permitted and started when the yaw rate Yr becomes equal to or greater than the start threshold value Hx of the dimension of the yaw rate Yr calculated using equation (8). That is, step S160 is affirmed at the time (calculation cycle) when "Yr≧Hx" is satisfied, and thereafter, the braking force Fx of each wheel WH is adjusted based on the turning amount deviation hY. That is, the start of the deflection suppression control is determined based on the yaw rate Yr, and the execution of the deflection suppression control is continued based on the turning amount deviation hY.

In the deflection suppression control, it is preferable that the driver's operation of a steering operation member (for example, a steering wheel) SW is taken into account. In this case, the turning amount deviation hY is employed as the deflection amount Hn. When the turning amount deviation hY becomes equal to or greater than the start threshold value Hx of the yaw rate dimension calculated using equation (8), execution of the deflection suppression control is started. That is, at the time (calculation cycle) when "hY≧Hx" is satisfied, step S160 is affirmed, and execution of the deflection suppression control is started. That is, the start (permission) of the deflection suppression control is determined based on the turning amount deviation hY, and the execution of the deflection suppression control is continued based on the turning amount deviation hY. Note that when the turning amount deviation hY calculated in the dimension (physical quantity) of the steering angle Sa is adopted as the deflection amount Hn, the threshold value Hx in the dimension of the yaw rate Yr is converted to the dimension of the steering angle Sa. Then, the starting threshold Hx is calculated (see equations (1) to (3)).

At the start of execution (operation permission) of deflection suppression control, any one of lateral acceleration Gy (detected value of lateral acceleration sensor GY), yaw rate Yr (detected value of yaw rate sensor YR), and turning amount deviation hY is determined to be deflected. It is adopted as the quantity Hn. Then, a starting threshold Hx corresponding to the adopted deflection amount Hn (that is, the same physical quantity) is calculated based on the vehicle speed Vx and the deceleration Ga. At the time when the deflection amount Hn becomes equal to or greater than the threshold value Hx (corresponding calculation cycle), deflection suppression control based on the turning amount deviation hY is started. In other words, when the vehicle is stopped by automatic braking control, the lateral movement distance Dh of the vehicle from the current moment until the vehicle stops is estimated based on the vehicle body speed Vx and the deceleration Ga. Then, the start threshold value Hx is determined as a value corresponding to the lateral movement distance Dh (based on a predetermined distance hd smaller than the lateral movement distance Dh). The start of execution of the deflection suppression control is determined by comparing "deflection amount Hn, which is a state quantity that can be detected or calculated (i.e., vehicle speed Vx, yaw rate Yr, lateral acceleration Gy, and steering angle Sa)" with a threshold value Hx. be done. Therefore, the adaptation for each vehicle type can be simplified and the number of adaptation steps can be reduced. Note that, since the predetermined distance hd used to calculate the threshold value Hx is smaller than the lateral movement distance Dh, the vehicle does not deviate from the road by exceeding the road edge LE such as a lane or shoulder.

<Action/Effect>
The configuration, actions and effects of the automatic braking device JS according to the present invention will be summarized.
The automatic braking device JS performs automatic braking control according to the required deceleration Gs. During automatic braking, if the vehicle is deflected due to unbalanced cargo, etc., each wheel WH is adjusted based on the turning amount deviation hY (the difference between the actual turning amount Ya and the standard turning amount Ys). The braking force Fx is adjusted, and deflection suppression control for suppressing the deflection of the vehicle is executed. In the automatic braking system JS, the start of execution of deflection suppression control is determined based on a threshold value Hx. Here, the threshold value Hx is a value based on the lateral movement distance Dh when the vehicle stops, and is determined based on the vehicle body speed Vx and the deceleration Ga. Specifically, in the automatic braking system JS, a deflection amount Hn representing the degree of deflection of the vehicle is calculated based on at least one of the lateral acceleration Gy and the yaw rate Yr, and the deflection amount Hn is set to a threshold value. Deflection suppression control is started when the value exceeds Hx. Since the threshold value Hx is determined (calculated) as a state variable that can be detected or calculated, adaptation for each vehicle type is simplified and can be easily performed. As a result, the man-hours (time) required for vehicle adaptation are reduced.

For example, in the automatic braking system JS, the deflection amount Hn is a turning amount deviation hY (the deviation between the standard turning amount Ys calculated based on the steering angle Sa and the actual turning amount Ya calculated based on the yaw rate Yr). Adopted. Further, a threshold value Hx is calculated (determined) as a physical quantity having the same dimension as the turning amount deviation hY, based on the vehicle body speed Vx and the deceleration Ga. Specifically, the threshold value Hx is calculated based on the value obtained by dividing the "square value of the deceleration Ga" by the "cubic value of the vehicle speed Vx" (i.e., "Ga ² /Vx ³ "). . When the turning amount deviation hY becomes equal to or greater than the threshold value Hx, deflection suppression control during automatic braking is started. Since the turning amount deviation hY is calculated based on the steering angle Sa, by employing the turning amount deviation hY as the deflection amount Hn, the steering operation (i.e., the steering angle Sa) is performed at the start of execution of the deflection suppression control. is taken into account. That is, by using the turning amount deviation hY, the driver's intention regarding steering is reflected at the start of the deflection suppression control. Further, the deflection suppression control is started based on the turning amount deviation hY, and the deflection suppression control is continued based on the turning amount deviation hY. In other words, since the start and continuation of control are performed using the same state quantity, continuity of control can be ensured in the deflection suppression control.

<Other embodiments>
Other embodiments will be described below. Other embodiments also provide the same effects as described above (facilitation and simplification of adaptation, ensuring continuity of control, etc.).

In the above embodiment, front and rear brake systems are used as the two brake systems. Instead of this, a diagonal type (also referred to as "X type") may be adopted. In this case, one of the two hydraulic chambers Rm is connected to the front right wheel cylinder CWi and the rear left wheel cylinder CWl, and the other of the two hydraulic chambers Rm is connected to the front left wheel cylinder CWj. , and connected to the right rear wheel cylinder CWk. Even in this case, the braking force Fx of each wheel WH is adjusted independently for each wheel by the pressure regulating valve UA, the inlet valve VI, and the outlet valve VO.

In the above embodiment, a hydraulic type actuator (fluid unit HU) via the brake fluid BF is exemplified as the actuator that adjusts the braking torque Tq (result, braking force Fx) to the wheel WH. Alternatively, an electric type driven by an electric motor may be used. In the electric actuator, the rotational power of the electric motor is converted into linear power, thereby pressing the friction member against the rotating member KT. Therefore, braking torque Tq is directly applied by the electric motor to generate braking force Fx, regardless of braking fluid pressure Pw. Furthermore, it may be a composite type in which a hydraulic actuator via brake fluid BF is used for the front wheels WHf, and an electric actuator is used for the rear wheels WHr.

JS...Automatic braking device, LE...Road edge, BP...Brake operating member, SW...Steering operating member, CM...Master cylinder, CW...Wheel cylinder, HU...Fluid unit (actuator), UA...Pressure regulating valve, ECU...Controller , GX...Deceleration sensor, GY...Lateral acceleration sensor, YR...Yaw rate sensor, SA...Steering amount sensor (steering angle sensor), Gx...Detected deceleration, Ge...Calculated deceleration, Ga...Actual deceleration, Vx...Vehicle body Speed, Gy...lateral acceleration, Yr...yaw rate, Sa...steering amount (steering angle), Ys...standard turning amount, Ya...actual turning amount, hY...turning amount deviation, Hn...deflection amount, Hx...start threshold, Fx...braking force.

Claims (3)

An automatic braking device for a vehicle that executes deflection suppression control that suppresses deflection of the vehicle during braking by adjusting the braking force of each wheel of the vehicle,
calculating a deflection amount representing the degree of deflection of the vehicle;
A threshold value for starting the deflection suppression control is determined based on a lateral movement distance of the vehicle from the current time until the vehicle stops, which is estimated from the vehicle body speed of the vehicle and the deceleration of the vehicle. ,
An automatic braking device for a vehicle that starts the deflection suppression control when the deflection amount becomes equal to or greater than the threshold value . The automatic braking device for a vehicle according to claim 1,
An automatic braking device for a vehicle, wherein the deflection amount is calculated based on a yaw rate of the vehicle, and the threshold value is determined based on a value obtained by dividing the square value of the deceleration by the cube value of the vehicle body speed. The automatic braking device for a vehicle according to claim 1,
An automatic braking device for a vehicle that calculates the deflection amount based on the lateral acceleration of the vehicle, and determines the threshold value based on a value obtained by dividing the square value of the deceleration by the square value of the vehicle body speed..